In a small internal combustion engine utilizing a carburetor, such as those engines in a lawnmower, a snowblower, or other outdoor power equipment, the engine may include a choke assembly that provides a rich fuel-air mixture for starting the engine and a throttle assembly responsive to the load on the engine. In many small engines, the choke assembly is acutated manually.
In engines having an automatic choke assembly, the choke opening can be controlled by a thermally responsive mechanism. For cold engine temperature conditions, such as when initially starting an engine, the choke valve reduces the air flow to the engine to enrich the air/fuel mixture. For higher temperature conditions, such as after normal engine operation (e.g. for a hot restart of the engine), the choke valve is not needed because the engine no longer requires a rich air/fuel mixture.